rz 


Circular  No   42,  Fifth  Edition 


United  States  Department  oT  Airricu-nvire, 

BUREAU   OK   KNTOMOI.OGY. 
I      0     HOWAIO  t:l«t  and  Chief  of  Bureau. 


now   TO  CONTROL  THE  s\\  JOSE  sc.ll,K. 

Bj    0.    1  .    M  mi  1 1  r. 

•/  ciw  f  iii  absence  »f  Chief. 

THE  SAN   JOSE    SCALE  A  PERMANENT  FACTOR    IN   FRUIT  GROWING. 

The  Ban  Joee  -  iridely  disseminated  and  has  become  so 

firmly  established  in  the  principal  deciduous-frail  regions  of  this 
country  that  its  extermination  is  now,  in  most  cases,  oul  of  the  ques- 
tion. In  the  main,  therefore,  the  San  Jose  scale  must  be  recognized  as 
a  permanent  factor  to  be  regularly  dealt  with  as  are  other  insect  evils 
or  the  fungous  die  I  plants. 

termination  is  possible  only  where  the  scale  is  detected  at  the  very 

t  on   new  or    recently  planted  nursery  stock  or  at    least  before  any 

considerable  chance  of  spread  has  been  afforded.     It  is  true  that  by 

the  greatest  care  in  the  introduction  of  nursery  stock  the  San  Jose  scale 
may,  for  years,  perhaps,  be   kept    out  of  districts  now  free  from  it,  and 

is  warranted,  therefore,  in  adopting  every  precaution  to  avoid 
introducing  this  Bcale  and  even  to  attempt  extermination  wherever  the 
conditions  are    reasonably  favorable.     There  is  only   one  method  of 

minating  the  Bcale,  and  that  is  by  digging  up  and  burning  all 
infest  •       This  is  an  heroic  remedy  and  is  advised  only  under  the 

condition-  of  very  recent  introduction  of  nursery  stock — in  other  words. 
where  the  scale  is  discovered  within  a  few  months  after  the  purchase 

of  the  infested  trees.      If  the  scale  has  passed  an  entire  hreedii 

in  an  orchard  it  will  have  spread  much  more  widely  than  any  inspec- 
tion will  indicate  and  very  likely  will  have  gained  a  footing  on  wild  and 
ornamental  plants  other  than  fruit  trees,  from  which  it  will  reintroduce 
itself  into  neighboring  orchards  or  into  new  plantings,  however  thorough 
may  have  been  the  attempts  to  .radicate  it. 
While,  therefore,  one  is  undoubtedly  justified  in  asserting  that  the  San 
permanency,  it  by  no  means  follows  that  the  profit- 
■■  th  of  deciduous  fruit<    is   seriously  menaced  on  this  account. 
The  experience  in  California,  covering  many  years,  and  in  the  Kast  now 
for  a  considerable  period,  lias  abundantly  demonstrated  that  this  scale 

:    can    he    controlled.      In    other  words,    by  proper   treatment,    the 

value  of  which  has  been  demonstrated  by  much  practical  experii 

an  orchard   may  he  protected   from   serious  injury  and    kept   in   a  good 

paying  condition  so  far  as  influenced  by  the  San  Jose  scale. 


THE   DIFFERENT    MEANS  OF    CONTROLLING  THE    SAN    JOSE   SCALE 

The  methods  of  control  which  have  been  especially  followed  in  the 
Eastern  States  are  (1)  the  application  of  the  lime-sulphur  wash,  (2) 
the  soap  treatment,  (3)  treatment  with  pure  kerosene,  (4)  treatment 
with  crude  petroleum,  (5)  treatment  with  mechanical  mixtures  of  either 
of  the  last  two  oils  with  water,  (6)  the  application  of  petroleum  emul- 
sion with  soap  and  (7)  miscible  oils.  All  of  these  methods  have  proved 
successful  against  the  San  Jose  scale  when  property  carried  out.  The 
lime-sulphur  wash  is,  however,  the  cheapest  and  safest  and  has  become 
the  standard  remedy  against  the  San  Jose  scale  in  commercial  orchard 
practice.  One's  choice  of  insecticide  must  be  governed  by  availability, 
special  needs,  and  experience.  In  the  main  these  remedies  are  winter 
treatments  and  may  be  employed  at  any  time  when  the  treee  are  in 
dormant,  leafless  condition.  The  weaker  oil-water  mixtures  and  the 
emulsions  maj',  however,  be  used  in  the  growing  season.  The  treat- 
ments enumerated  are  all  for  trees  in  the  orchard.  Nursery  stock  badly 
enough  infested  to  require  such  treatment  is  best  destroyed.  For  the 
general  disinfection  of  nursery  stock  the  hydrocyanic-acid-gas  treatment 
is  the  standard  and  only  satisfactory  means. 

THE    LDIE-SULPHUR    WASH. 

In  California,  where  the  San  Jose  scale  first  appeared, "the  standard  remedy 
against  it  is  the  lime-sulphur-salt  wash,  a  mixture  formerly  used  as  a  sheep  dip  in 
Australia  and  employed  with  little  change  against  the  San  Jose  scale.  Thisw;ish 
was  naturally  first  thought  of  on  the  discovery  of  the  San  Jose  scale  in  eastern 
orchards.  The  earlier  tests,  however,  conducted  by  this  office  in  1894,  gave 
unfavorable  results,  and  the  experimentation  which  followed  resulted  in  the 
demonstration  of  several  distinct  and  valuable  methods  of  control  noted  below. 
Later  studies  of  the  action  of  this  wash  in  California  led  the  writer  in  1900  to 
give  it  a  further  careful  trial  in  the  East,  with  most  successful  results,  dem- 
onstrating that,  with  favoring  conditions,  i.  e.,  absence  of  dashing  rains  for  a 
few  days  after  the  application,  it  would  give  just  as  good  results  in  the  Eastern 
States  as  on  the  Pacific  coast.  A  year  later  (1901-2)  very  elaborate  tests  con- 
ducted by  Doctor  Forbes  in  Illinois  showed  that  fairly  hard  rains  will  not  always 
invalidate  spraying  with  this  mixture.  A  vast  amount  of  experience  of  the  most 
practical  kind  since  gained,  contributed  to  by  all  the  eastern  experiment  stations 
and  by  the  big  commercial  fruit  growers  of  the  Middle  and  Eastern  States,  has 
fully  demonstrated  the  practical  merit  of  this  wash  and  its  superiority  to  others 
in  point  of  safety  to  trees  and  in  cheapness.  Its  disadvantages  are  the  difficulty 
of  preparation  and  the  heavy  wear  which  it  entails  on  apparatus— objections, 
however,  which  do  not  offset  its  notable  advantages,  particularly  for  commercial 
orchard  work  or  where  the  number  of  trees  to  be  treated  is  sufficient  to  warrant 
the  trouble  of  its  preparation.  It  is  in  fact  the  standard  spray  now  used  in  com- 
mercial orchards  for  the  San  Jose  scale. 

Composition  and  preparation. — In  the  matter  of  composition  of  the  wash, 
scarcely  any  two  experimenters  agree.  Salt  was  a  part  of  the  original  composi- 
tion of  the  sheep  dip  and  has  long  been  retained,  with  the  idea  that  it  added, 
perhaps,  to  the  caustic  qualities,  and  particularly  to  the  adhesiveness  of  the 
wash.     For  the  latter  purpose  a  very  small  amount  only,  1  or  2  pounds  to  the 


btuhel  of  lime,  need  be  added,  following  tl  In  the  preparation  of  white- 

wash miztnree.     In  practical  experience,  however,  the  bave  been 

hi  wry  little  benefit  and  li  therefore  omitted  in  the  formula  non  given.    The 
proportion  i>f  lime  and  sulphur  is  a  matter  of  some  indifference.    The  mi 
obtained  is  sulphld  of  lime,  and  if  an  excess  of  lime  Is  need  it  simply  remains 
undissolved  in  the  mixture  and  adds  to  the  whitewashing  charactei  of  the  appli- 
cat  inn.    Too  much  lime  is  distinctly  objectionable,  however,  because  of  the  gi 
difficulty  of  Bpraying  and  harder  wear  on  the  pump  and  nosalea.    The  formula 

lubetantially  tl ue  which  has  been  hitherto  recommended  bj 

Bureau,  reduced  to  the  H5  or  SO  gallon  basis,  01  the  capacity  of  the  ordinar) 
-•■in-  barrel  commonly  used  in  Its  preparation  by  the  steam  method. 

Unslaked  lime  pounds  20 

Flowers  Of  sulphur  iln  I". 

Water  to  make  gallons      r>  to  50 

The  Sowers  of  sulphur,  although  requiring  somewhat  longer  cooking,  Beems 
to  make  a  better  wash  than  ground  sulphur,  but  the  latter  may  in-  employed. 
Stone  lime  of  good  quality  should  be  secured  and  Blaked  in  a  small  quantity  of 
water,  Bay,  one-third  the  full  dilution.  The  Bulphur,  previously  mixed  up  into 
a  stiff  paste,  Bhould  be  added  at  once  to  the  slaking  lime.  The  whole  mixture 
should  be  boiled  for  at  least  one  hour,  either  in  an  iron  kettle  over  a  fire  out  of 
doors  or  in  barrels  by  steam.  Prolonged  boiling  increases  the  percentage  of  the 
higher  Bulphids,  but  the  practical  end  is  obtained  by  boiling  for  the  time  indi- 
cated. In  the  process  of  making,  the  color  changes  from  yellow  to  the  clear 
brown  of  Bulphid  of  lime,  except  for  the  excess  of  lime  Boating  in  it.  After  an 
hour's  boiling  the  full  quantity  of  cold  water  may  be  added,  and  the  mixture 
should  then  be  promptly  applied  In  order  to  get  its  full  strength  before  the  higher 
Bulphids  are  lost  by  cooling  and  crystallizing  out.  In  transferring  to  the  spray 
tank  it  Bhould  be  passed  through  an  iron  screen  or  strainer,  and  the  tank  itself 
should  be  provided  with  an  effective  agitator. 

.  -The  wash  is  a  winter  application  and  can  not  he  applied 
to  trees  in  leaf.  It  may  be  applied  at  any  time  after  the  falling  of  foliage  in 
early  winter  and  prior  to  the  swelling  of  the  buds  in  spring.  The  later  the  appli- 
cation can  be  made  the  better  the  results,  and  the  best  period  is  just  before  the 
buds  swell  in  March  or  April.  It  will  probably  be  necessary  also  to  make  this 
application  every  year,  or  at  least  as  often  as  the  San  .lose  scale  develops  in  any 
numbers.  The  wash  kills  the  San  Jose  scale  not  only  by  direct  caustic  action, 
hut  also  by  leaving  a  limy  coating  on  the  trees,  which  remains  in  evidence  until 
midsummer  or  later  and  kills  or  prevents  the  Bettling  of  young  scale  i: 
which  may  come  from  parents  escaping  the  winter  action. 

The  wear  on  pumps  and  nozzles  can  be  kept  to  a  minimum  by  carefully  wash- 
ing the  apparatus  promptly  after  use.  The  Vermorel  nozzle  is  the  beet  one  for 
the  wash,  and  additional  caps  may  be  secured  to  replace  worn  ones.  The  use 
of  an  air  or  other  gas  pressure  pump  instead  of  the  ordinary  liquid  pump  will 
save  the  wear  of  the  lime  on  the  pump.  In  spraying  with  this  wash  clothing  is 
ruined,  and  only  the  oldest  garments  should  he  worn.  Care  should  be  taken 
also  to  protect  the  eyes  to  avoid  unnecessary  inflammation. 

-s.— This  wash  is  distinctively  the  remedy  for  the  San  Jose 
scale  and  is  particularly  effective  in  applications  to  the  smooth-bark  fruit 
such  as  peach,  pear,  and  plum.  In  the  case  of  the  apple  the  terminal 
twigs  are  often  covered  with  a  fuzzy  growth,  more  pronounced  in  some  varieties 
than  others,  which  prevents  the  wash  from  properly  coating  the  bark.  The 
young  from  scale  insects  which  escape  destruction  at  such  points,  for  the  reason 
indicated  or  from  imperfect  spraying,  are  driven  out  onto  the  new  growth,  or, 


in  the  case  of  fruit  spurs,  onto  the  fruit,  so  that  a  tree  on  which  the  scale  lias 
been  pretty  thoroughly  exterminated  may  nevertheless  present  badly  spotted 
fruit.1  In  such  cases  the  additional  use  of  some  one  of  the  oil  sprays  may  be 
necessary. 

This  wash  is  of  nearly  equal  value  against  closely  allied  scale  pests,  such  as 
Forbes's  scale  and  the  West  Indian  peach  scale,  and  late  sprayings  are  quite 
effective  against  the  scurfy  scale  and  the  oyster-shell  scale.  Other  insect  pests 
which  winter  on  the  bark  or  about  the  buds  are  destroyed  by  it. 

In  addition  to  this  range  of  usefulness  against  insect  pests  this  wash  has  shown 
itself  to  be  a  valuable  fungicide,  notably  for  the  peach  leaf  curl,  sprayed  trees 
being  practically  immune  from  this  disease,  so  that  the  cost  of  treatment  in  the 
case  of  the  peach  is  often  more  than  made  good  by  the  fungicidal  benefit  alone. 
Later  experience  indicates  its  usefulness  also  as  a  winter  application  for  apple 
scab  and  possibly  for  other  plant  diseases. 

THE    SOAP   TREATMENT. 

Whale-oil  or  fish-oil  soap,  preferably  made  with  potash  lye,  is  dissolved  in 
water  by  boiling  at  the  rate  of  2  pounds  of  soap  to  the  gallon  of  water.  If 
applied  hot  and  on  a  comparatively  warm  day  in  winter,  it  can  be  easily  put  on 
trees  with  an  ordinary  spray  pump.  On  a  very  cold  day,  or  with  a  cold  solution, 
the  mixture  will  clog  the  pump,  and  difficulty  will  be  experienced  in  getting  it 
on  the  trees.  Trees  should  be  thoroughly  coated  with  this  soap  wash.  Pear 
trees  and  apple  trees  may  be  sprayed  at  any  time  during  the  winter.  Peach 
trees  and  plum  trees  are  best  sprayed  in  the  spring,  shortly  before  the  buds 
swell.  If  sprayed  in  midwinter  or  earlier,  the  soap  solution  seems  to  prevent 
the  development  of  the  fruit  buds,  and  a  loss  of  fruit  for  one  year  is  apt  to  be 
experienced,  the  trees  leafing  out  and  growing,  however,  perhaps  more  vigor- 
ously on  this  account.  The  soap  treatment  is  perfectly  safe  for  all  kinds  of  trees 
and  is  very  effective  against  the  scale.  With  large  trees  or  badly  infested  trees, 
preliminary  to  treatment  it  is  desirable,  with  this  as  well  as  other  applications, 
to  prune  them  back  very  rigorously.  This  results  in  an  economy  of  spray  and 
makes  much  more  thorough  and  effective  work  possible.  The  soap  may  be 
secured  in  large  quantities  at  from  34  cents  to  4  cents  a  pound,  making  the  mix- 
ture cost,  as  applied  to  the  trees,  from  7  cents  to  8  cents  a  gallon.  The  success 
of  the  soap  treatment  is  largely  influenced  by  the  character  of  the  soap  used. 
Many  brands  are  on  the  market,  mostly  made  with  soda  lye.  A  potash  soap 
should  be  insisted  on,  and  one  that  does  not  contain  more  than  30  per  cent  of 
water.  The  soda  soap  washes  are  apt  to  be  gelatinous  when  cold  and  difficult 
or  impossible  to  spray  except  when  kept  at  a  very  high  temperature. 

OIL   WASHES  AND  EMULSIONS. 

The  scale  washes  enumerated  under  this  heading,  in  which  petroleum  is  the 
principal  ingredient,  are  often  more  available  for  limited  work  than  the  lime- 
sulphur  wash.  The  precautions  noted  under  each  should  be  carefully  attended 
to,  as  otherwise  serious  damage  may  result. 

Kerosene  treatment. — The  kerosene  treatment  consists  in  spraying  the  trees 
with  ordinary  illuminating  oil  (coal  oil  or  kerosene).  The  application  is  made 
at  any  time  during  the  winter,  preferably  in  the  latter  part,  and  by  means  of  a 
spray  pump  making  a  fine  mist  spray.  The  application  should  be  made  with 
the  greatest  care,  merely  enough  spray  being  put  on  the  plant  to  moisten  the 
trunk  and  branches  without  causing  the  oil  to  flow  down  the  trunk  and  collect 

'See  Bui.  46,  Bur.  Ent.,  U.  S.  Dept.  Agr.,  p.  .34. 


about  the  baas.    With  the  use  of  tbii  substance  it  must  be  constantly  born*  in 
mind  thai  careless  or  excessive  application  ol  the  oil  will  be  vi  • 
treated  plant.    The  application  should  be  made  on  ■  bright,  dry  d 
the  oil  will  evaporate  ai  qulcklj  ble.    <>»  ■  moist,  olondy  day  the  evap- 

oration i-  riow,  ana  injury  to  the  planl  is  more  apt  to  reenlt.     If  the  kei 
itment  be  adopted,  therefore,  it  must  be  with  ■  fall  appred  the  fad 

that  the  death  of  the  tree  maj  follow  ,    Tin-  oil  hai  I d  need, however,  ■  great 

many  timet  and  verj  extensively  without  |  tenl   injory  of  any  kind.    On 

the  other  ban. I,  it>  carelesi  use  hai  frequently  killed  valuable  trees,     fti  advan- 

Itfl  effectiveness,  its  availability,  and  it-  oheapnec 

rapidlj  ana4  much  lew  of  H  being  required  to  wet  the  tree  than  of  a  soap 

and  water  Bpray.    Pure  kai  more  apt  to  be  injurious  to  peach  and  plum 

than  to  pear  and  apple  trees,  and  the  treatment  of  the  former,  as  with  the  soap 

,,  should  be  deferred  until  spring,  just  before  the  buds  iwell.    With  young 

treea  espeelaUy  it  is  well  to  mound  up  about  the  trunk  a  few  inches  of  earth  to 

oaten  the  overflow  of  oil,  removing  the  oil-soaked   earth   immediately  after 

itment. 

n  treatment.— Crude  petroleum  i-  used  in  . 'Mirth 
way  as  is  the  common  illuminating  oil  referred  to  above,     It-  advantage  over 
kerosene  is  that,  a-  it  contains  a  very  large  percentage  of  the  heavy  oil-,  it  does 
nut  penetrate  the  hark  so  readily,  ami,  on  the  other  hand,  only  the  light  oils 
evaporate,  leaving  a  coating  of  the  heavy  oils  on  the  hark,  whirl  in 

lence  for  months  and  prevents  any  young  scale,  which  may  come  from  the 
chance  individuals  that  were  not  reached  by  the  spray,  from  getting  a  foothold. 
Crude  petroleum   comes  i„  a   great    many  different   form-,   depending  upon  the 

ility,  the  -tad.'  successfully  experimented  with  in  the  work  of  this  Bureau 

ring  IS     r.aume.     Crude  oil  Bhowing  a  lower  Baume  than  IS    is  un-afe.  and 

n„ .re  than  t~>   ,s  nnneoessarily  high.    The  lower  specific  gravity  indicated  1 1 
ibetantially  that  of  the  refined  product,  the  removal  of  the  lighter  oils  in 

ning  practically  offsetting  the  removal  of  the  paraffin  and  vaseline.  The  same 
cautions  and  warnings  apply  to  the  crude  SB  to  the  refined  oil. 

„l-,r„t.r  treatment.  —Various  pump  manufacturers  have  placed  on  the 
market  Bpraying  machines  which  mechanically  mix  kerosene  or  crude  petroleum 
with  water  in  the  act  of  spraying.  The  attempt  is  to  regulate  the  proportion  of 
kerosene  bo  that  any  desired  percentage  of  oil  may  he  thrown  out  with  the  w 
and  he  broken  up  by  the  nozzle  into  a  sort  of  emulsion.  Some  of  these  machi; 
when  everything  is  in  good  working  order,  give  fairly  satisfactory  results,  hut 
absolute  reliability  is  far  from  assured.    The  lust  outlook  for  good  apparatus 

this  s„rt  seem-  to  be  in  carrying  the  oil  and  water  in    separate   line-  of   h,,- 
tbe  nozzle,  uniting  them    in  the  latter,  and  in  maintaining  an  absolute  equality 
of  pres.-ure  on  both  the  oil  and  the  water  tanks  by  employing  compressed  air  as 
the  motive  force,  kept  up  by  an  air  pump,  the  air  chamber  communicating  with 
both  of  the  liquid  receptacles.     I  toe  or  more  manufacturers  are  now  working  on 

apparatu-  of  this  general  description.  A  LO-per-cent-strength  kerosene  may  be 
used  for  a  summer  sprav  on  trees  where  the  San  Jose  scale  is  multiplying  rapidly 
and  where  it  is  not  desirable  to  let  it  go  unchecked  until  the  time  for  the  winter 
treatment.  The  winter  treatment  with  the  water-keroeene  sprays  may  be  made 
at  a  -trength  of  20  per  cent  of  the  oil.  Applications  of  the  oil-water  spray 
Should  be  attended  with  the  same  precautions  as  with  the  pure  oil,  and  there  is 
even  somewhat  greater  risk,  owing  to  the  natural  tendency  one  has  to  apply 
the  dilute  mixture  much  more  freely  than  the  pure  oil.  The  application  should 
be  merely  enough  to  wet  the  bark  and  should  not,  to  any  extent,  at  least,  run 
down  the  trunk.  The  collection  of  water  and  oil  about  the  trunk  is  just  as 
dangerous  to  the  the  pure  oil. 


6 

In  the  use  of  the  oil  sprays  noted  above,  one  who  has  had  no  experience  with 
them  is  advised  to  make  some  careful  preliminary  tests  to  fully  master  the 
process,  preferably  waiting  two  or  three  weeks  to  determine  the  results  before 
entering  on  a  general  treatment  of  the  orchard.  It  is  well,  also,  with  the  oil- 
water  mixtures  to  test  the  pump  from  time  to  time,  spraying  into  a  glass  jar  or 
bottle  to  determine  by  actual  measurement  whether  the  correct  percentages  of 
oil  and  water  are  being  maintained. 

Petroleum-soap  emulsions.— The  kerosene-soap  emulsion,  following  chiefly  the 
Riley-Hubbard  formula,  has  been  one  of  the  standard  means  against  scale  insects 
for  twenty  years.  The  dislillate  emulsion  generally  employed  in  California  for 
spraying  citrus  trees,  on  which  the  lime-sulphur  wash  can  not  be  used,  is  sub- 
stantially the  same  thing,  except  that  it  is  made  with  the  California  distillate  or 
petroleum  oil.  Crude  petroleum  of  any  kind,  as  well  as  the  refined  product, 
may  also  be  used  in  making  this  emulsion.  The  use  of  the  soap  emulsion 
against  the  San  Jose  scale  in  the  East  has  not  been  very  general  on  account  of 
the  greater  facility  with  which  the  pure  oil  or  oil-water  mixtures  can  be  applied. 
The  difficulty  of  obtaining  uniform  results  with  the  latter  has  led  to  a  return  to 
the  use  of  emulsions  to  some  extent,  and  there  can  be  no  doubt  about  their 
superior  merit  when  it  is  desired  to  dilute  the  pure  oils.  Emulsions  may  be 
applied  at  any  strength  with  absolute  confidence  that  there  will  be  no  variation. 
Where  the  emulsion  can  be  prepared  wholesale  by  steam  power,  its  employment 
is  attended  with  no  difficulties.  In  California  it  is  prepared  by  oil  companies 
and  sold  at  very  slightly  more  than  the  cost  of  the  oil  and  soap  ingredients.  It 
is  made  after  the  following  formula: 

Petroleum gallons.  _     2 

Whale-oil  soap  (or  1  quart  soft  soap) pound-,     i 

Water  (soft) gallon. _     1 

The  soap,  first  finely  divided,  is  dissolved  in  the  water  by  boiling  and  immedi- 
ately added  boiling  hot,  away  from  the  fire,  to  the  oil.  The  whole  mixture  is 
then  agitated  violently  while  hot  by  being  pumped  back  upon  itself  with  a  force 
pump  and  direct  discharge  nozzle  throwing  a  strong  stream,  preferably  one- 
eighth  inch  in  diameter.  After  from  three  to  five  minutes'  pumping  the  emulsion 
should  be  perfect,  and  the  mixture  will  have  increased  from  one-third  to  one- 
half  in  bulk  and  assumed  the  consistency  of  cream.  Well  made,  the  emulsion 
will  keep  indefinitely  and  should  be  diluted  only  as  wanted  for  use. 

In  limestone  regions,  or  where  the  water  is  very  hard,  some  of  the  soap  will 
combine  with  the  lime  or  magnesia  in  the  water,  and  more  or  less  of  the  oil  will 
be  freed,  especially  when  the  emulsion  is  diluted.  Before  use,  such  water  should 
be  broken  with  lye,  or  rain  water  should  be  employed. 

For  winter  sprays  dilute  the  emulsion  with  either  3,  4,  or  5  parts  of  water,  giv- 
ing a  percentage  of  oil  approximately  17,  13,  and  11  per  cent.  The  strength  in 
oil  of  this  application  on  trees  as  compared  with  the  oil-water  sprays  is  the  equiv- 
alent of  25,  20.  and  15  per  cent  oil,  because  relatively  more  of  the  heavier  oil- 
soap  emulsion  is  held  by  the  bark.  The  two  stronger  mixtures  may  be  used  on 
apple  and  pear  and  the  weaker  one  on  peach  and  plum. 

For  summer  applications  dilute  with  7, 10,  or  15  parts  of  water,  giving  approxi- 
mately 8,  6,  and  4  per  cent  of  oil.  The  weaker  strengths  may  be  used  on  trees 
with  tender  foliage,  such  as  that  of  peach,  and  the  greater  strength  for  strong 
foliage  plants,  like  the  apple  and  pear. 

Miscible  oils.— It  will  be  noted  that  the  difficulty  to  be  overcome  in  the  use  of 
oils  is  to  effect  their  dilution  to  render  them  harmless  to  the  plant.  The  dilu- 
tion is  effected  with  great  accuracy  by  the  kerosene-soap  emulsion,  and  less 
accurately  by  the  mechanical  emulsions  of  oil  and  water.     There  have  appeared 


daring  the  last  fevi  oible  oils,  which  readily  ami  per- 

manently mix  with  water,  andean  be  applied  "  Ith  the  lame  readiness  and 

trengtb  ai  the  emulsions  ol  p.    These  oils  have  i"i 

their  principal  ingredients  some  form  of  petroleum  rendered  soluble  bj  the  addi- 
tion of  a  percentage  of  vegetable  oil  and  ''Hi  or  saponified  with  an  alkali,  and 
they  are,  in  fact,  a       I         tjuid  petroleum  ->>.ii>.    The]  I  under  various 

trade  names.    They  have  i  in-  disadva  I  deal  more  than  the 

standard  emulsions  <t  the  lime-sulphui   wash,  but   have  thi    great  advs 

nu  always  ready  for  immediate  use  withoul  troublesome  preparation. 
The)    can  not   be  diluted    for   winter  application!  with 

more  than  10  or  15  pan-  of  wab  i  te,  and  ti  me  danger 

of  injury  to  the  trees  if  they  are  can  pplied.    The)  have, 

however,  a  very  osefnl  place,  and  especially  as  furnishing  insecticide 

where  onlj  s  fen  trees  arc  to  be  treated  and  the  owner  would  probably  not  u<< 

tn  the  trouble  of  preparing  an  emulsion  01  the  lit Bulphur  wash.    They  have 

been  so  far  principally  used  against  the  Ban  Jose  scale  as  dormant  tree  washes. 

FUMIGATION  OK  NURSERY  STOCK. 

All  nursery  stock  which  is  under  the  least  suspicion  of  contamination 
with  the  San  Jose  scale  Bhould  be  fumigated  ;  and  it  is  perhaps  worth 
while  to  fumigate  in  any  case  to  give  the  iit iii« •  - 1  assurance  of  Bafety  to 
the  purchaser.  The  hydrocyanic-acid-gas  fumigation  is  the  one  to  upe. 
This  gas  is  generated  by  combining  potassium  cyanid,  Bulphuric  acid, 
ami  water.  The  proportions  of  the  chemical.-,  are  a-  follows :  Refined 
potassium  cyanid  (98  per  cent),  1  ounce;  commercial  Bulphuric  acid, 
1  ounce;  water.  :'.  fluid  ounces — to  ev.ry  LOO  cubic  feet  of  space  in  the 
fumigating  room  or  house.     The  latter  should  be  as  nearly  air-tight   as 

ble  and  provided  with  means  of  ventilation  above  and  at  the  Bide, 
Operated  from  without,  so  that  at  the  end  of  the  treatment  the  poison- 
ous L'a-es  may  he  allowed  to  escape  without  thi  iity  of  anyone 
entering  the  chamber.  The  generator  of  the  gas  may  he  any  glazed 
earthenware  vessel  of  I  or  2  gallons  capacity,  and  should  he  placed  on 
the  floor  of  the  fumigating  room.  The  water  should  first  be  poured  into 
it,  then  the  acid,  and  lastly  the  cyanid  should  he  added,  preferably  in 
lumps  the  size  of  a  walnut.  Promptly  after  adding  the  cyanid  the 
room  should  he  vacated  and  the  door  made  fast.  The  treatment  Bhould 
continue    forty    minute-.      //    must    hi    borni    in    mind   Unit   lli<    (/us    is 

nely   poisonous   and   must   "/"/</•   //<<   circumstances   h<>    inhaled. 

gas  treatment  is  effective  also  against  the  scale  on  growing  trees  in 
the  orchard  ;  hut  the  difficulty  and  expense  of  the  treatment,  except  for 
nursery  stock,  make  it  prohibitive  in  the  case  of  deciduous  fruits. 

Appro  ■ 

Jamks  Wilson, 

s  Tetary  of  Agriculture. 

Washington,  P.  C,  February  t3,  IS 

O 


UNIVERSITY  OF  FLORIDA 


3  1262  09216  4812 


I 


